RESUMO
Huntington's disease (HD) is an autosomal-dominant neurodegenerative disorder caused by a polyglutamine expansion in the amino-terminal region of the huntingtin protein, which promotes progressive neuronal cell loss, neurological symptoms and death. In the present study, we show that blockade of mGluR5 with MTEP promotes increased locomotor activity in both control (Hdh(Q20/Q20)) and mutant HD (Hdh(Q111/Q111)) mice. Although acute injection of MTEP increases locomotor activity in both control and mutant HD mice, locomotor activity is increased in only control mice, not mutant HD mice, following the genetic deletion of mGluR5. Interestingly, treatment of mGluR5 knockout mice with either D1 or D2 dopamine antagonists eliminates the increased locomotor activity of mGluR5 knockout mice. Amphetamine treatment increases locomotor activity in control mice, but not mGluR5 null mutant HD mice. However, the loss of mGluR5 expression improves rotarod performance and decreases the number of huntingtin intranuclear inclusions in mutant HD mice. These adaptations may be due to mutant huntingtin-dependent alterations in gene expression, as microarray studies have identified several genes that are altered in mutant, but not wild-type HD mice lacking mGluR5 expression. qPCR experiments confirm that the mRNA transcript levels of dynein heavy chain, dynactin 3 and dynein light chain-6 are altered following the genetic deletion of mGluR5 in mutant HD mice, as compared with wild-type mutant HD mice. Thus, our data suggest that mutant huntingtin protein and mGluR5 exhibit a functional interaction that may be important for HD-mediated alterations in locomotor behavior and the development of intranuclear inclusions.
Assuntos
Modelos Animais de Doenças , Doença de Huntington/patologia , Corpos de Inclusão Intranuclear/patologia , Atividade Motora/fisiologia , Receptor de Glutamato Metabotrópico 5/fisiologia , Proteínas da Membrana Plasmática de Transporte de Serotonina/fisiologia , Animais , Western Blotting , Proliferação de Células , Células Cultivadas , Perfilação da Expressão Gênica , Doença de Huntington/genética , Doença de Huntington/metabolismo , Técnicas Imunoenzimáticas , Corpos de Inclusão Intranuclear/genética , Corpos de Inclusão Intranuclear/metabolismo , Camundongos , Camundongos Knockout , Atividade Motora/efeitos dos fármacos , Piridinas/farmacologia , RNA Mensageiro/genética , Reação em Cadeia da Polimerase em Tempo Real , Receptor de Glutamato Metabotrópico 5/antagonistas & inibidores , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Tiazóis/farmacologiaRESUMO
OBJECTIVE: Preclinical and clinical studies have shown that serotonin levels might modulate susceptibility to seizures. Here we evaluated an association between 5HTTLPR and 5HTTVNTR allele variants in serotonin transporter gene and epileptogenesis in temporal lobe epilepsy (TLE). METHODS: A case-control candidate gene study evaluating the frequencies of 5HTTLPR biallelic and 5HTTVNTR allele variants in patients and healthy subjects. Genotypes were grouped according to transcriptional efficiency. Cases were 175 patients with TLE selected from the Epilepsy Outpatient Clinic of Hospital de Clínicas de Porto Alegre, classified according to the electroclinical classification of the ILAE and neuroimaging findings. The control group consisted of 155 healthy unrelated subjects selected from the same population. RESULTS: We observed that less efficient transcriptional genotypes for 5-HTT polymorphisms were more frequent in epileptic patients (O.R.=3.24; 95% C.I.=1.08-9.73; p=0.036). Our results suggest that less efficient transcriptional genotypes for serotonin transporter gene are associated with TLE. CONCLUSION: In this study we observed an association between the presence of 5HTTLPR and 5-HTTVNTR less transcriptional efficient combined genotypes and TLE. Our results suggest that modulation of the serotoninergic system might be implied in epileptogenesis in TLE.
Assuntos
Região 5'-Flanqueadora/genética , Epilepsia do Lobo Temporal/genética , Repetições Minissatélites/genética , Polimorfismo de Nucleotídeo Único , Proteínas da Membrana Plasmática de Transporte de Serotonina/genética , Adulto , Alelos , Brasil/epidemiologia , Estudos de Casos e Controles , Epilepsia do Lobo Temporal/epidemiologia , Feminino , Frequência do Gene , Estudos de Associação Genética , Genótipo , Humanos , Masculino , Mutagênese Insercional , Deleção de Sequência , Proteínas da Membrana Plasmática de Transporte de Serotonina/fisiologia , Transcrição Gênica , Adulto JovemRESUMO
1. The serotonin transporter (SERT) handles serotonin (5-hydroxytryptamine (5-HT)) and is blocked by the antidepressant SERT inhibitors fluoxetine and fluvoxamine. Although the importance of SERT in the central nervous system is clear, SERT also functions in the peripheral vasculature. In the present study, we tested the hypothesis that the vasculature from female rats has increased SERT function compared with male rats because females are more responsive to SERT inhibitors. 2. In addition to in vitro experiments, in vivo experiments were used to evaluate how male and female rats handle chronically elevated levels of 5-HT. Wild-type (WT) and SERT-knockout (SERT-KO) rats were infused with 5-HT (25 µg/kg per min) for 7 days by minipump. 3. Using HPLC analysis, we demonstrated that blood vessels (aorta, carotid artery, jugular vein and vena cava) from naïve, non-infused female rats took up 5-HT acutely in vitro in a SERT-dependent manner. In in vitro experiments, SERT affected the contractility of aortas from female rats, as evidenced by an eightfold increase in potency of 5-HT in fluvoxamine (1 µmol/L)-incubated WT aortas compared with control. Fluvoxamine did not alter 5-HT-induced contraction in aortas from SERT-KO female rats. 4. Infusion of 5-HT resulted in an increase in tissue 5-HT that was reduced to a larger extent in blood vessels from female than male SERT-KO rats. Aortic contractions to 5-HT were abolished in aortas from male and female 5-HT-infused SERT-KO rats compared with WT rats. 5. Collectively, these data suggest that SERT function, when challenged with 5-HT, is modestly more important in the vasculature of the female compared with male rat.